Mastering A&P Lecture Homework Chapter 9-11

The molecular interaction described as a cross bridge involves the binding of which two proteins?

A and C. Cross bridges between thin and thick myofilaments are formed by the specific interaction between actin (A) and myosin head groups (C).

Which step precedes all of the other listed steps?

ACh is released by the motor neuron. The first step toward generating a skeletal muscle contraction is nervous stimulation of the muscle fiber in order to generate an action potential. the site of muscle stimulation, where the nerve ending communicated with the muscle fiber, is called the neuromuscular junction.

The mechanism by which the neurotransmitter is returned to a presynaptic neuron's axon terminal is specific for each neurotransmitter. Which of the following neurotransmitters is broken down by an enzyme before being returned?

Acetylcholine

Which of the following is true of axons?

A neuron can have only one axon, but the axon may have occasional branches along its length.

A postsynaptic cell can be a neuron, a muscle cell, or a secretory cell. What is an example of a presynaptic cell?

A neuron.

In which phase in the figure would the net movement of Ca2+ into the sarcoplasmic reticulum (SR) be greatest?

C. During the period of relaxation (C), Ca2+ is transported by active transport into the SR. Decreased Ca2+ concentrations in the sarcoplasm leads to detachment of cross bridges and, consequently, decreased contractile force.

Which structure in the figure corresponds to a single muscle cell?

C. Note that a skeletal muscle cell is commonly termed a muscle fiber.

Which muscle has a unipennate arrangement of fascicles?

C. The extensor digitorum longus inserts into only one side of the tendon, giving it a unipennate arrangement.

Which muscle inserts on the greater tubercle of the humerus?

C. The infraspinatus typically originates on the infraspinous fossa of the scapula and inserts into the greater tubercle of the humerus posterior to the insertion of supraspinatus.

Which protein functions as a motor protein that applies the power stroke during muscle contraction?

C. The myosin head groups (C) hydrolyze ATP to power molecular movement along the actin subunits of the thin myofilaments.

Which of the following is most directly required to initiate the coupling of myosin to actin?

Ca+ Binds to troponin, which removes tropomyosin from the myosin binding site on actin.

Which muscle is innervated by the S3 nerve, S4 nerve, and the inferior rectal nerve (a branch of the pudendal nerve)?

D. The levator ani muscles are innervated by several nerves including the pudendal, white the other muscles indicated are innervated by the pudendal nerve alone.

Which muscle provides a guide to the position of the radial artery at the wrist for taking the pulse?

D. The radial pulse can easily be found between the tendons of the flexor carpi radialis and brachioradialis.

Which of the cell types shown is most associated with the production and flow of cerebrospinal fluid (CSF)?

D. These cells line central cavities of the CNS and, in certain places, produce CSF. The cilia of these cells help circulate the CSF that nourishes and cushions the brain and spinal cord.

Which muscle is an antagonist to the biceps brachii muscle?

D. Triceps brachii extends the forearm, white the biceps brachii flexes it.

In a bedridden patient recovering from a badly fractured femur, disuse atrophy in the thigh muscles is caused by _________.

Decreased synthesis of muscle proteins and/or increased breakdown of muscle proteins. Muscle tissue grows and heals in response to stress. Without the stress of exercise and normal daily activities, muscle tissue degenerates.

Which of the following events would be directly affected if a neuron had a mutation that prevented the production of voltage-gated Na+ channels?

Depolarization leading to action potentials

An action potential is self-regenerating because __________.

Depolarizing currents established by the influx of Na+‎ flow down the axon and trigger an action potential at the next segment.

Which of these structures is surrounded by the connective tissue sheath known as the perimysium?

B. The structure at B is covered by the perimysium. Remember that the word root peri means around as in the perimeter.

Which of the muscles indicated by letters has action at only one joint?

B. This muscle originates on the humerus and extends to the ulna, so it only has action at the elbow joint.

The hamstrings consist of three muscles located on the posterior thigh. Why is it recommended that a caregiver squat using these muscles to help a patient sit down?

Because it prevents back muscle strain.

What benefit would an improved muscle tone from strengthening the quadriceps femoris muscles provide?

Better-stabilized knee joint.

Which of the following statements is NOT true regarding ATP production in muscles during periods of prolonged energy use, such as exercise?

In the absence of oxygen, creatine phosphate can drive aerobic respiration pathways for a few minutes. This is not true for a few reasons. First, creatine phosphate directly phosphorylates ATP instead of providing any support for aerobic pathways. Second. creatine phosphate stores are used up in about 15 seconds. Third, a cell doesn't need an oxygen deficit for creatine phosphate to be activated; it just needs to be short on ATO.

What is the action of the muscle identified by the letter A?

It abducts and medially rotates the thigh and steadies the pelvis. It is an extremely important muscle for walking. This is the action of the gluteus medius muscle.

If the cell could no longer produce ATP, what would the effect be on the sarcoplasmic reticulum?

It would be unable to concentrate Ca+ in the sarcoplasmic reticulum. To concentrate Ca+ in the sarcoplasmic reticulum, active transport must occur. With no ATP, there would be no active transport.

During the hyperpolarization phase of the action potential, when the membrane potential is more negative than the resting membrane potential, what happens to voltage-gated ion channels?

K+ channels close. Na+ channels go from an inactivated state to a closed state.

Which of the following is the clearest example of a neuronal membrane's selective permeability?

K+ ions can diffuse across the membrane more easily than Na+ ions.

During an action potential, hyperpolarization beyond (more negative to) the resting membrane potential is primarily due to __________.

K+ ions diffusing through voltage-gated channels

The repolarization phase of the action potential, where voltage becomes more negative after the +30mV peak, is caused primarily by __________.

K+ ions leaving the cell through voltage-gated channels

The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____.

K+; Na+

Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?

Leak channels.

Which of the following muscles is named for its action?

Levator labii superioris. Elevating the upper lip.

Which of the following factors influence the velocity and duration of muscle contraction?

Load placed on the muscle. Speed (velocity) of shortening is a function of load and muscle-fiber type. Contraction is fastest when the load on the muscle is 0; a greater load results in a slower contraction and a shorter duration of contraction.

Predict the possible effect of a drug that totally blocks the neurotransmitter receptor on the postsynaptic membrane. For example, curare is a neurotoxin used by several South American cultures. The primary effect of curare is that acetylcholine, a major neuromuscular neurotransmitter, cannot bind at its receptor because curare is blocking it. Predict the possible effects of curare on the postsynaptic membrane and muscle.

Local graded potential and action potential transmission is blocked, and there is no response by the postsynaptic cell, the muscle.

What event directly triggers the release of neurotransmitters shown in A?

Diffusion of Ca2+ into the axon terminal. A nerve impulse arrives at the axon terminal triggering the opening of Ca2+ channels, which allows for the diffusion of Ca1+ into the terminal. This in turn leads directly to the release of neurotransmitters by exocytosis.

Which pathway for regenerating ATP is the most inefficient during 30 minutes of light to moderate exercise?

Direct phosphorylation of ADP by creatine phosphate. This rapid ATP-synthesizing pathway only lasts for about 15 seconds.

Why does the action potential only move away from the cell body?

The areas that have had the action potential are refractory to a new action potential.

The resting membrane potential depends on two factors that influence the magnitude and direction of Na+ and K+ diffusion across the plasma membrane. Identify these two factors.

The presence of concentration gradients and leak channels.

During action potential propagation in an unmyelinated axon, why doesn't the action potential suddenly "double back" and start propagating in the opposite direction?

The previous axonal segment is in the refractory period.

Isometric contractions are important contractions that allow humans to hold their posture over time.

True. Muscle produces enough tension to support the skeleton, but not move it, creating the conditions for posture in humans.

The anterior compartment of the thigh is involved in lower leg extension.

True. The quadriceps group sits in the anterior compartment of the thigh. These muscles extend the lower leg.

The Na+-K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped?

Na+ is pumped out of the cell and K+ is pumped into the cell.

Which of the following does NOT describe conditions that occur during an action potential?

Na+ is used to repolarize the membrane.

What prevents the Na+ and K+ gradients from dissipating?

Na+-K+ ATPase.

Name the muscle at A.

Orbicularis oculi. Sphincter muscle of the eyelid that surrounds the rim of the orbit.

What component of the reflex arc determines the response to a stimulus?

integration center

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,

ion channels in the plasma membrane of the receiving neuron open.

Which of the following is expected to occur first if the membrane potential increase shown in the graph on the left were to reach the threshold value indicated at −55 mV?

opening of voltage-gated Na+ channels

In the brain, vision originates in the rods and cones in the retina. Separate regions of the brain decode basic information, like color, shapes, intensity of light, and there are other regions that decode information like position in space, and awareness of patterns. As you use your visual system, all of these regions are working simultaneously. This simultaneous awareness of all regions working at the same time is due to which processing pattern listed below?

parallel processing

Which of the following choices best represents synaptic transmission?

presynaptic axon to synapse to dendrite or postsynaptic cell body

Which neuron circuit pattern is involved in the control of rhythmic activities such as breathing?

reverberating circuit

Which of the following circuit types is involved in the control of rhythmic activities such as the sleep-wake cycle, breathing, and certain motor activities (such as arm swinging when walking)?

reverberating circuits

Events that occur during synaptic activity are listed here, but they are arranged in an incorrect order. Choose the correct order of these events below. (a) Voltage-gated calcium channels open (b) Neurotransmitter binds to receptors (c) Action potential arrives at axon terminal (d) Neurotransmitter is removed from the synaptic cleft (e) Neurotransmitter released into synaptic cleft (f) Graded potential generated in postsynaptic cell

(c) Action potential arrives at axon terminal (a) Voltage-gated calcium channels open (e) Neurotransmitter released into synaptic cleft (b) Neurotransmitter binds to receptors (f) Graded potential generated in postsynaptic cell (d) Neurotransmitter is removed from the synaptic cleft

What is the value for the resting membrane potential for most neurons?

-70 mV

The smallest contractile unit within skeletal muscle would correspond to the distance between which 2 points in the figure?

1 and 7. The distance between points 1 and 7 spans a sarcomere, the smallest contractile unit of a muscle fiber.

What is the magnitude (amplitude) of an action potential?

100 mV

The region between which 2 points corresponds to the entire A (dark) band?

2 and 6. The A band, AKA the dark band, is occupies by the entire length of thick myofilaments.

What type of channel on the postsynaptic membrane binds neurotransmitter?

A chemically gated channel.

Which protein is indicated by the letter A?

Actin. Actin is the chief component of the thin myofilaments.

Which of the following mechanisms is most significant in returning the ion concentrations to the resting state (from point D to point E)?

Active transport by the Na+-K+ pump

How is an action potential propagated along an axon?

An influx of sodium ions from the current action potential depolarizes the adjacent area.

Which functional group has the major responsibility for countering a specific movement?

Antagonists. Opposes the movement produced by the agonist. Often responsible for returning a limb to its initial position. Adjust the action of their agonists by contracting slightly to provide some resistance, this helping to prevent overshooting the mark or to slow or stop the movement. These pairs are located on opposite sides of the joint across which they act.

Where are action potentials regenerated as they propagate along a myelinated axon?

At the nodes of Ranvier

Where in the neuron is an action potential initially generated?

Axon hillock.

Which of the following interactions must occur first so that the others can take place?

B binds to troponin. Binding of calcium (B) to troponin removes the blocking action of tropomyosin along the thin myofilament. This allows myosin to bind to actin and form the cross bridge illustrated in this figure.

At which point of the illustrated action potential would voltage-gated Na+ channels be mostly open but voltage-gated K+ channels be mostly closed?

B.

Identify the gluteus maximus muscle.

B.

Which of the following letters represents the infraspinatus muscle?

B.

Which of the following letters represents the sartorius muscle?

B.

Which of the following corresponds to a single fascicle?

B. A fascicle is an organized group of muscle fibers (cells) bounded by a perimysium.

Which of the cell types shown helps determine capillary permeability in the CNS?

B. Extensions from these cells wrap capillaries and provide extra control over which materials enter or leave the intercellular fluid of the CNS.

In which phase of the muscle twitch shown in the figure would the maximum amount of ATP be consumed by myosin head groups?

B. Myosin heads catalyze the hydrolysis of ATP to power the sliding of myofilaments. This event would be at a maximum during the period of contraction (B).

Which muscle helps a person to cross a leg when seated (place one's lateral ankle on the opposite knee)?

B. Sartorius laterally rotates and abducts the thigh, which would both be necessary in placing one ankle on the opposite knee when sitting.

Which muscle tenses the skin of the neck and assists in depression of the mandible?

B. The platysma muscle tenses the neck skin and aids in depressing the mandible. It originates in the fascia of the upper chest.

Which of the following joint muscles is correctly matched with its lever type?

Biceps brachii at the elbow; third-class lever. In this case, the force is applied by the biceps brachii between the fulcrum, the elbow joint ad the load, which is the forearm.

Which of the following is a hamstring muscle?

Biceps femoris. The hamstrings are fleshy muscles of the posterior thigh (biceps femoris, semitendinosus, and semimembranosus). They cross both the hip and knee joints and are prime movers of thigh extension and knee flexion.

Which muscle is represented by the letter D?

Biceps femoris. This is the lateral hamstring.

Which statement accurately describes the event indicated by B?

Binding of acetylcholine to a receptor triggers the opening of an ion channel. Binding of acetylcholine to its receptor opens chemically (ligand) gated ion channels that allow Na+ and K+ to diffuse across the sarcolemma.

Which areas of this neuron would be classified as receptive regions?

Both A and B. The dendrites and soma of the cell receive signals from other neurons.

Which of the following statements is true of both membrane potential responses shown in the graphs?

Both responses are examples of graded potentials.

The primary function of the deep muscles of the thorax, such as the intercostals, is to promote __________.

Breathing. The deep muscles of the thorax, like the internal and external intercostals and the diaphragm, promote movements necessary for breathing.

Which of the following membrane regions would have significant numbers of voltage-gated ion channels?

C and D.

Identify the extensor digitorum longus muscle.

C.

In which area of the neuron is an action potential initially generated?

C. Axon hillock.

Identify the palmaris longus muscle.

C. Inserts into fascia of the palm and acts to tense the skin of the palm during hand movement. Missing in over 10% of humans.

What ion is entering the axon terminal at A, and what effect does it have?

Ca2+, which then causes release of neurotransmitter from the axon terminal

What is the role of calcium in synaptic activity?

Calcium influx into the synaptic terminal causes vesicle fusion.

How would the receptors at C best be classified?

Chemically gated

Which component has a role in the postsynaptic cell during synaptic activity?

Chemically gated channels

Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane.

Chemically gated; postsynaptic

Identify the action of the muscle at A.

Compress the abdomen. The transverse abdominis muscles are the deepest of the abdominal wall. They compress the abdominal contents.

What type of conduction takes place in unmyelinated axons?

Continuous conduction.

Which of the following are correctly matched?

Convergent arrangement of fascicles; fan-shaped muscle. A convergent muscle has a broad origin, and its fascicles converge toward a single tendon of insertion. Such is triangular or fan shaped like the pectoralis major muscle of the anterior thorax.

At which of the points along the illustrated action potential can a second action potential be produced, but only with a stimulus significantly greater than the one that produced the first?

D.

Identify the levator ani muscle.

D. Important in the support of the pelvic organs during various activities that put stress upon it, such as coughing and vomiting.

Which muscle would be a prime mover of knee extension?

D. Originates at coxal bone and inserts at the patella.

Which muscle originates on the pubic crest and symphysis and inserts on the xiphoid process and costal cartilages of ribs V through VII?

D. The rectus abdominus originates on the pubic crest and symphysis and inserts on the xiphoid process and costal cartilages of ribs V-VII.

Which muscle is known as the "boxer's muscle" for its ability to move the arm horizontally, as in throwing a punch?

D. The serratus anterior can be used to violently pull the scapula laterally and thus pull the shoulder forward, adding strength to a horizontal punch.

Which muscle is the prime mover of dorsiflexion?

D. The tibialis anterior is the only indicated muscle that is a prime mover of dorsiflexion.

Which of the following is a factor that determines the rate of impulse propagation, or conduction velocity, along an axon?

Degree of myelination of the axon

Which of the following muscles is shown on this image but is NOT indicated with a letter?

Deltoid.

What is the structure at A?

Dendrite.

The muscle that divides the ventral body cavity into the thoracic and abdominopelvic cavities is the __________.

Diaphragm.

Which description of synapses is not correct?

Direct signaling involves the activation of G proteins. Indirect signaling involves intracellular second messenger molecules, typically via G protein pathways. Direct signaling involves neurotransmitters that bind to ligand-gated ion channels and leads directly to changes to the polarization of the membrane.

The sliding filament model of contraction states that __________.

During contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree. In a relaxed muscle fiber, the thick and thin myofilaments overlap only at the ends of the A band.

Which of the neuroglial cell types shown are found in the peripheral nervous system (PNS)?

E. The cell shown in E wraps and insulates the soma of neurons within ganglia in the PNS.

A muscle that is lengthening while it produces tension is performing a(n) __________ contraction.

Eccentric. During isotonic, eccentric contractions, muscle lengthens as it generates tension, but not enough force, to overcome the load. We use eccentric contractions to lower objects (such as lowering a book from the shelf or lowering a barbell during a bench press).

Binding of the neurotransmitter to its receptor causes the membrane to __________.

Either depolarize or hyperpolarize

Muscle tissue can be stimulated by the nervous system. Cells with the ability to change their membrane potential have what property?

Excitability. AKA responsiveness, is the ability to receive and respond to a stimulus. For example, skeletal muscle contracts in response to receiving chemical stimulation from the CNS.

By which method does the structure at B release neurotransmitter?

Exocytosis

Neurotransmitter is released from presynaptic neurons through what mechanism?

Exocytosis.

What cellular event is indicated by A?

Exocytosis. Neurotransmitters stored in synaptic vesicles are released into the synaptic cleft by exocytosis.

More Na+ than K+ leaks through neuron membranes because of the properties of the non-gated leak channels.

False. K+ leak channels allow almost 25 times more K+ than Na+ to leak through the neuron membrane.

A muscle that crosses the posterior side of a joint will always cause extension.

False. Most of the time this is correct. There are 2 exceptions, the knee and the ankle. These joints are reversed because of rotation during development.

The longer a muscle is when it starts contracting, the more tension it can generate in the contraction.

False. Maximum muscle contraction occurs in an intermediate range for the muscle where there is both a good number of cross bridges that can form and room for the sarcomere to shorten. If a muscle is too long, there will not be enough cross bridges that can form to generate tension.

Which description of a muscle action is NOT correct?

Fixators hold joints in place, so movement does not occur. Ficators do hold a bone in place; however, they provide a stable base for a prime mover to create movement.

Which of the following muscles is named for its size?

Gluteus maximus.

What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?

Inactivation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open.

Myasthenia gravis is sometimes treated medically by a treatment that involves ____________.

Inhibiting the action of acetylcholinesterase. This enzyme breaks down acetylcholine into acetic acid and choline.

Where do most action potentials originate?

Initial segment.

What is the name and origin of the muscle at A?

Ischiocavernosus; ischial tuberosities. Ischiocavernosus retards venous drainage and maintains the erection of the penis or clitoris. It originates at the ischial tuberosities and inserts into the crura of the penis or clitoris.

Cross bridge formation between myosin heads and actin molecules is caused by the elevation of calcium ion concentration in the cytosol. During rigor mortis, this elevation of calcium ion concentration in the cytosol is permanent because _____________.

Mitochondria stop producing ATP molecules required by the sarcoplasmic reticulum's calcium ion pumps. A pump is considered an active transport process. Active transport moves molecules against their concentration gradient, which requires energy in the for of ATP.

Which of the following pairings does not fit?

Multipolar neurons: peripheral nervous system sensory neurons. Unipolar neurons function as sensory neurons in the PNS.

What structural classification describes this neuron?

Multipolar.

Which term best identifies a muscle cell?

Muscle fiber. Skeletal muscle cells fuse during development to form the mature, multinucleated muscle fibers.

In which type of axon will velocity of action potential conduction be the fastest?

Myelinated axons with the largest diameter.

Which protein is indicated by the letter E?

Myosin. Myosin tail groups form the extended regions of the thick myofilament.

The diffusion of what ion, across the neuronal membrane, is responsible for the local currents that depolarize regions of the axon to threshold?

Na+ (sodium)

The concentrations of which two ions are highest outside the cell.

Na+ and Cl-

The concentrations of which two ions are highest outside the cell?

Na+ and Cl−

What is happening to voltage-gated channels at this point in the action potential?

Na+ channels are inactivating, and K+ channels are opening.

Which of the following correctly states the direction followed by the specified ions when their voltage-gated channels open?

Na+ ions move into the axon; K+ ions move out.

During the action potential of a neuron, which ion is primarily crossing the membrane during the depolarization phase, and in which direction is the ion moving?

Na+ is entering the cell.

In multiple sclerosis, the cells that are the target of an autoimmune attack are the _________.

Oligodendrocytes

You are working on a new medication to selectively kill cancer cells. You test the drug on a culture of normal neurons to check for any side effects. Despite the presence of the drug, a normal resting membrane potential of −70 mV is maintained. Look at each of the figures below to analyze how the drug might be affecting the neuron. Figure A shows neuron activity under normal, or control, conditions (without the drug). Figure B shows neuron activity that has been altered due to exposure to the drug. Based on these results, the drug is most likely __________.

Preventing Na+-gated channels from opening.

How do action potential propagation speeds compare in myelinated and unmyelinated axons?

Propagation is faster in myelinated axons.

What is the function of the filaments found in ranges 1-2 and 6-7 but no other ranges?

Protection from overstretching. Elastic (titin) filaments help to protect the muscle from overstretching and also aid in returning it to normal length.

Slow oxidative muscle fibers are best suited for __________.

Running a marathon.

The node-to-node "jumping" regeneration of an action potential along a myelinated axon is called __________.

Saltatory conduction

The _________ shorten(s) during muscle contraction.

Sarcomere. As actin slides over myosin, the z lines are pulled closer together, shortening the sarcomere.

Name the glial cell at F.

Schwann cell.

Which of the following peripheral nervous system (PNS) neuroglia form the myelin sheaths around larger nerve fibers in the PNS?

Schwann cells. Schwann cells (also called neurolemmocytes) surround all nerve fibers in the PNS and form myelin sheaths around the larger fibers. Myelin protects and electrically insulates nerve fibers, and it increases the transmission speed of nerve impulses.

Which of the following is NOT a normal function of muscle tissue?

Secreting hormones. Function of the endocrine system.

Which of the following are correctly paired?

Skeletal muscle; voluntary control

Which is the main receptive portion of the neuron?

The dendrite.

Which organelle can chemically regulate the shortening of the muscle?

The sarcoplasmic reticulum.

The myelin on myelinated neurons can be degraded or destroyed in diseases such as multiple sclerosis-a process called demyelination. If a myelinated neuron was affected by demyelination, how would this affect action potentials in that neuron?

The speed of action potential propagation would be slower.

What change in a neuron is being measured in the graph?

The voltage measured across the axon membrane at a specific point as an action potential travels past

The plasma membrane is much more permeable to K+ than to Na+. Why?

There are many more K+ leak channels than Na+ leak channels in the plasma membrane.

What is the basic condition when a neuron is described as polarized?

There is a separation of positive and negative charges across a membrane.

Suppose that both stimuli seen in these graphs happened equally at the same time on a postsynaptic membrane as a result of two different synapses. Which of the following best describes the result?

There would be little or no graded potential.

An enzyme known as acetylcholinesterase is present in the synaptic cleft. What is its role?

To break down acetylcholine. Acetylcholinesterase breaks acetylcholine apart, terminating the synaptic transmission. Choline can be taken back into the axon terminal and reused.

Two muscles in this image, identified by the letters C and D, share a function. What is that function?

To close the jaw. The muscles at C and D originate on the skull and insert on the mandible. They exert powerful forces during chewing (elevation of the mandible).

Local anesthetics block voltage-gated Na+ channels, but they do not block mechanically gated ion channels. Sensory receptors for touch (and pressure) respond to physical deformation of the receptors, resulting in the opening of specific mechanically gated ion channels. Why does injection of a local anesthetic into a finger still cause a loss of the sensation of touch from the finger?

Touch stimulation of this sensory receptor will open the mechanically gated ion channels, but action potentials are still not initiated because propagation of an action potential requires the opening of voltage-gated Na+ channels.

The main forearm extensor is the __________.

Triceps brachii.

The interaction between which protein and ion initiates contraction of skeletal muscle?

Troponin and calcium ions. When calcium binds to troponin, troponin changed shape and moves tropomyosin away from its inhibitory position. As a result, the energized myosin heads can bind to the actin molecules and begin the cross bridge cycle, which shortens the muscle fiber.

Bundles of axons in the central nervous system are called tracts.

True.

If the neuron membrane becomes more permeable to Na+, Na+ will transport across the membrane, causing the cell to depolarize.

True.

Opening K+ or Cl- channels in a postsynaptic membrane would produce an inhibitory postsynaptic potential (IPSP).

True.

ATP is required to cause the power stroke in the myosin head.

True. ATP is required to re-cock the myosin head so that is can generate a second power stroke.

In the muscles of the limbs, the origin is usually the immobile muscle attachment.

True. In the muscles of the limbs, the insertion is pulled toward the immobile origin.

What condition will increase the diffusion of molecules, such as neurotransmitters?

an increase in the amount of neurotransmitter exocytized by the presynaptic axon

Identify the correct sequence of the following events. (a) Myosin generates a power stroke. (b) Ca+ binds to troponin. (c) ATP recharges the myosin head. (d) Troponin removes tropomyosin from G actin. (e) The sarcomere shortens. (f) Myosin binds to actin.

b, d, f, a, e, c. The Ca+ binds to troponin, which removes the tropomyosin from actin. This allows the myosin to bind to actin and generate a power stroke, shortening the sarcomere. ATP is used to recharge the myosin.

During depolarization, which gradient(s) move(s) Na+ into the cell?

both the electrical and chemical gradients

Which of the following stimuli caused the reaction in the graph on the left?

opening of gated Na+ channels

Which of the following is NOT a type of circuit?

pre-synaptic circuits

The box labeled D illustrates three mechanisms by which the effects of a neurotransmitter may be terminated. Which of the following mechanisms is NOT included in the figure?

reuptake of the neurotransmitter by transport into the postsynaptic cell

If a signal from a sending neuron makes the receiving neuron more negative inside,

the receiving neuron is less likely to generate an action potential.

When calcium ions enter the synaptic terminal,

they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.

The velocity of the action potential is fastest in which of the following axons?

A small myelinated axon.

What type of event is required for an action potential to be generated?

A threshold level depolarization

Which letter represents the biceps brachii muscle?

A.

Which muscle is a prime mover of arm abduction?

A.

Destruction of which of the neuroglial cell types leads to the disease multiple scleroses (MS)?

A. The defects in nerve transmission associated with MS are caused by a loss of myelin within the CNS.

Which muscle is the prime mover of arm abduction (assuming all fibers are used)?

A. The deltoid muscle has three sets of fibers. If all three are activated, the arm is abducted at the shoulder.

Which of the neuroglial cell types shown form myelin sheaths within the CNS?

A. These cells form myelin sheaths within the white matter of the CNS.

Which glial cells have the most diversity of function?

Astrocytes. Astrocytes are the most abundant and diversely functioning glial cells. Examples of their many functions include: anchoring neurons to capillaries, aiding in the exchanges between neurons and blood, guiding the migration of young neurons, and helping control the chemical environment around neurons.

During what part of the action potential do voltage-gated Na+ channels begin to inactivate (their inactivation gates close)?

At the end of the depolarization phase, as the membrane potential approaches its peak value.

What is the major role of the Na+-K+ pump in maintaining the resting membrane potential?

Maintaining the concentration gradients for Na+ and K+ across the cell membrane.

Muscles A through D all have an origin in common-- what is it?

Medial epicondyle of humerus. All of the labeled muscles share this origin, although some have additional ones. This position of origin is important so that these muscles may function properly whether the forearm is supinated or pronated.

Which statement best describes exocytosis?

Membrane organelles fuse with the membrane and release contents out of the cell.

Which of the following types of glial cells monitors the health of neurons, and can transform into a special type of macrophage to protect endangered neurons?

Microglia. Microglial cells are small and ovoid with relatively long "thorny" processes. Their processes touch nearby neurons, monitoring their health, and when they sense that certain neurons are injured or are in other trouble, the microglial cells migrate toward them. Where invading microorganisms or dead neurons are present, the microglial cells transform into a special type of macrophage that phagocytizes the microorganisms or neuronal debris.

What level of structural organization do voltage-gated sodium channels in muscle sarcolemma represent?

Molecule.

Which of the following would increase the membrane permeability to K+?

More K+ leakage channels.

Each neuron shown in this figure innervates a group of muscle fibers. What is the term for a group of muscle fibers innervated by a single neuron?

Motor Unit.

Ependymal cells line many open cavities in the central nervous system (CNS). Ependymal cells have cilia on the side of the cell that face these openings. What is the most likely function of these ciliated cells?

Movement and circulation of cerebrospinal fluid.

What is the direct role of neurotransmitter at a chemical synapse?

Neurotransmitter binds to receptors on the postsynaptic cell membrane and allows ions to diffuse across the membrane.

A molecule that carries information across a synaptic cleft is a

Neurotransmitter.

If both motor neurons shown in this figure were to develop action potentials and stimulate muscle fibers, would all the muscle cells shown here contract?

No, because neurons in this figure do not innervate every muscle cell shown. Only 5 muscle fibers shown are innervated. The others would not contract unless they were stimulated by other neurons that are not shown.

Duchenne muscular dystrophy could theoretically be cured if a technique was developed that would __________.

None of the above. Duchenne muscular dystrophy is caused by a mutation in the dystrophin gene. Without a normal copy of DNA for transcription, there can never be a normal protein translated. This genetic mutation causes the protein to be either abnormal in structure or completely absent.

What characterizes repolarization, the second phase of the action potential?

Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.

Which of the following does NOT describe the process of summation?

One EPSP fails to bring the cell to threshold.

Let's consider a scenario in which the resting membrane potential changes from −70 mV to +70 mV, but the concentrations of all ions in the intracellular and extracellular fluids are unchanged. Predict how this change in membrane potential affects the movement of Na+. The electrical gradient for Na+ would tend to move Na+ __________ while the chemical gradient for Na+ would tend to move Na+ __________.

Out; in.

Which of the following is INCORRECTLY paired?

Pectoralis major; arm abduction. This adductions the arm.

In a synapse, neurotransmitters are stored in vesicles located in the __________.

Presynaptic neuron

Which of the following movements demonstrates a first-class lever?

Raising your head up off your chest. The posterior neck muscles provide the effort, the antlanto-occipital joint is the fulcrum, and the weight to be lifted is the facial skeleton.

If both of the neurons in the figure were activated, more muscle fibers would contract than if either neuron alone were active. This mechanism for control of the force of muscle contraction is known as __________.

Recruitment. The increased force generated by the activation of increasing numbers of motor units.

Which muscle acts as both a knee (leg) extensor and hip (thigh) flexor?

Rectus femoris. The quadriceps femoris (group of four muscles) is a powerful knee extensor. One of the quadriceps, rectus femoris, also acts as a hip flexor.

Which of the following are correctly matched?

Rectus; straight. Rectus means straight.

Which of the following is NOT one of the basic functions of the nervous system?

Release hormones into the bloodstream that travel around the systemic blood circulation to communicate with cells in multiple locations within the body. Hormones are released by endocrine organs. The nervous system does have some control over endocrine function, but the endocrine system is considered a separate signaling system.

Excitation-contraction coupling includes all EXCEPT which of the following events?

Release of acetylcholine from axon terminals at the neuromuscular junction. Release of acetylcholine from axon terminals at the neuromuscular junction is an event that precedes excitation-contraction coupling, which begins with excitation of the T-tubules.

Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference?

Resting membrane potential (RMP).

In addition to diffusion, what are two other mechanisms that terminate neurotransmitter activity?

Reuptake and degradation

Which of these muscles is visible in the figure but NOT indicated by a letter?

Serratus anterior. Originates on ribs I-VIII and inserts on the anterior surface of the vertebral border of the scapula. It interdigitates with the external oblique.

Which of the following statements is FALSE?

Skeletal muscle cells use creatine phosphate instead of ATP to do work. Muscle cells, just like other cells, use ATP to do work. Creatine phosphate is used by muscle cells to directly phosphorylate ADP to resynthesize ATP.

Which type of muscle requires voluntary nervous stimulation for activation?

Skeletal. In order to contract, skeletal muscle fibers must be voluntarily stimulated by the nervous system. The site of muscle stimulation, where the nerve fiber communicates with the muscle fiber is called the neuromuscular junction.

Hyperpolarization results from __________.

Slow closing of voltage-gated K+ channels.

Which muscle-fiber type is best suited for endurance activities, such as long-distance jogging?

Slow oxidative fibers. Best suited for endurance activities because they produce ATP aerobically and are fatigue-resistant.

Which of the following best characterizes depolarization?

Small, consecutive steps of Na+ penetration into the axon along its length

Why is the body position of both a post-surgical patient and the caregiver critical in performing a safe patient move from bed to chair?

So that lifting leverage can be properly applied.

Which of the following statements is correct regarding the polarization of a neuronal membrane and the formation of a resting membrane potential?

Sodium/Potassium pumps maintain concentration gradients; sodium and potassium move down their concentration gradients through leakage channels.

What division of the nervous system is most specifically responsible for voluntary motor control?

Somatic nervous system. The somatic nervous system is composed of somatic motor nerve fibers that conduct impulses from the central nervous system to skeletal muscles. It is often referred to as the voluntary nervous system because it allows us to consciously control our skeletal muscles.

The major head flexor muscles are the __________.

Sternocleidomastoid muscles. The sternocleidomastoid muscles flex and laterally rotate the head. Acting alone, each muscle rotates the head toward the shoulder on the opposite side and tilts or laterally flexes the head to the shoulder on the same side.

Which rotator cuff muscle is correctly paired with its action?

Subscapularis; medial rotation. The subscapularis originates on the subscapular fossa and inserts on the anterior surface of the head of the humerus. The lesser tubercle of the humerus is pulled toward the subscapular fossa, which leads to medial rotation.

The small space between the sending neuron and the receiving neuron is the

Synaptic cleft.

The connective tissue that covers structure A is continuous with which of the following?

Tendon. The dense connective tissue at A is continuous with the tendon that connects the muscle to a bone or, in some cases to another muscle or to the skin.

Which of the following is NOT a rotator cuff muscle?

Teres major. Teres major is not one of the four rotator cuff muscles, which include supraspinatus, infraspinatus, teres minor, and subscapularis. Their main function is to reinforce the capsule of the shoulder and rotate the humerus in the glenoid cavity.

Which of the following best describes the Na+ and K+ concentrations across a neuron's plasma membrane?

The Na+ concentration is higher outside the cell compared to inside. The K+ concentration is higher inside the cell compared to outside.

Tetraethylammonium (TEA) blocks voltage-gated K+ channels such that K+ cannot pass even when the channels are open. However, TEA leaves K+ leakage channels largely unaffected. How would you expect the action potential to change if you treated a neuron with TEA?

The action potential would depolarize as usual, but the repolarization phase would take longer, causing the action potential to be more broad in time.

The force of a muscle contraction is NOT affected by __________.

The amount of ATP stored in the muscle cells. The force of muscle contraction is not affected by the amount of ATP stored in the muscle cells. Instead of relying on storage of ATP, muscle cells use ATP regenerating pathways, such as glycolysis, to meet the aTP demands of muscle contraction.

Many neurons have many short, branching extensions called dendrites. What is the benefit of these structures for a neuron?

The dendrites provide a large surface area for connections from other neurons.

Which of the following muscles does the phrenic nerve innervate?

The diaphragm. The phrenic nerve innervates the diaphragm. The intercostal nerves innervate the intercostal muscles. The sternocleidomastoid muscles are innervated by the accessory nerves.

Which criterion is used to functionally classify neurons?

The direction in which the nerve impulse travels relative to the central nervous system.

In a lab you are conducting tests with various chemicals and neurotransmitter receptors. You notice that exposed frog muscle cells depolarize when you add the chemical nicotine to the acetylcholine (ACh) receptors. What does this tell us about the relationship between neurotransmitters and their receptors?

The effect of a neurotransmitter is based on the properties of the receptor more than the neurotransmitter.

Imagine you changed the concentration of K+ outside a neuron such that the resting membrane potential changed to -80 mV (from the normal resting value of -70 mV). What have you changed?

The electrical gradient for K+ and the concentration gradient for K+.

One action potential in a motor neuron causes the full reaction in skeletal muscle, which is called a twitch. One twitch can generate max tension in a muscle. Are these statements true or false?

The first statement is true; the second statement is false. One action potential causes a single muscle twitch. However, a single twitch would not generate any meaningful tension in a skeletal muscle.

Where are the origins of most of the muscles that move the fingers?

The forearm.

An action potential in one segment of axon causes adjacent sections of axon membrane to reach threshold through what mechanism?

The generation of local currents.

Which of the following statements is FALSE?

The hamstrings are prime movers of hip (thigh) flexion and knee (leg) flexion. The hamstrings are prime movers of hip (thigh) extension, not hip flexion. They are also prime movers of knee (leg) flexion.

Why does regeneration of the action potential occur in one direction, rather than in two directions?

The inactivation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just fired an action potential.

On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you?

The inside surface of the plasma membrane is much more negatively charged than the outside surface.

A toxin released by certain bacteria can block the release of neurotransmitters into a neuromuscular synapse. What would result from such a block?

The loss of ability to contract the muscle. Without acetylcholine, the muscle would not be able to contract or even maintain tone.

Which of the following is NOT a difference between graded potentials and action potentials?

The magnitude of action potentials decrease as the impulse travels further away from the start of the impulse while graded potentials do not decrease in magnitude.

What characterizes depolarization, the first phase of the action potential?

The membrane potential changes from a negative value to a positive value.

What event triggers the generation of an action potential?

The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.

Which of the following statements most accurately describes the effect caused by binding of the neurotransmitter (green dots) to the structure labeled C?

The membrane potential of the postsynaptic membrane changes.

Based on what you know of the relationship between the thick and the thin filaments, what would happen if a disorder existed that caused a person to produce no tropomyosin?

The muscle tissues would never be able to relax. The tropomyosin covers the myosin binding site on actin. Without tropomyosin, the myosin would constantly have access to those binding sites.

What result would be expected if an additional stimulus, equal in intensity to the first, were to be applied to the muscle at the 60 millisecond (ms) time point?

The muscle would increase in tension to a level greater than that measured at the beginning of phase C. The second, more forceful contraction that would occur by adding another stimulus before the muscle has completely relaxed is and example of wave summation.

What is the function of the myelin sheath?

The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.

Which of the following is NOT used as a criterion for naming muscles?

The nervous system's control of the muscle. Whether the muscle is controlled by the involuntary or voluntary nervous system is not a criterion used for naming muscles.

You discover that a new chemical compound interacts with K+ voltage-dependent channels. What would be the effect on a neuron if the chemical came into contact with the axonal membrane?

The neuron would be unable to repolarize.

In a myelinated axon, how do the nodes of Ranvier differ from other segments of the same axon?

The nodes are more permeable to ions.

Which of the following statements is correct?

The number of muscle fibers best determines how powerful a muscle will be. More fibers means more power.

The repolarization phase of an action potential results from __________.

The opening of voltage-gated K+ channels.

Which of the following regions best identifies where myosin would have maximum cross-bridge access to actin?

The region between 2 and 3. Actin and myosin are components of thin and thick filaments, respectively. The region between points 2 and 3 includes the area of overlap between thin and thick filaments.

Hypothetically, what would be the most immediate effect of doubling the number of Na+ leakage channels in the plasma membrane?

The resting membrane potential would become less negative (more positive).

Suppose a drug is developed that blocks K+ leakage channels. The drug prevents ions from passing through those channels. If this drug was applied to a neuron, what would be the most immediate effect on that neuron?

The resting membrane potential would become less negative (more positive).

The contractile, or functional, unit of a muscle fiber is __________.

The sarcomere. The contractile unit of a muscle fiber and the smallest functional unit of a muscle. A sarcomere is the region of a myofibril between 2 successive Z discs; it primarily consists of thin and thick myofilaments.

What is the electrochemical gradient of an ion?

The sum of the electrical and concentration gradients for that ion.

As you start working out, you notice that your heart rate and breathing rate start to increase. Which division of your nervous system is generating this response? Be as specific as possible.

The sympathetic division of the autonomic nervous system. The sympathetic division of the autonomic, or involuntary, nervous system consists of visceral motor nerve fibers that regulate the activity of smooth muscles, cardiac muscles, and glands. This division is responsible for generating actions required during activity.

Which of these materials or structures would be found in greatest amounts or numbers at E?

Vesicles containing neurotransmitter.

An action potential releases neurotransmitter from a neuron by opening which of the following channels?

Voltage-gated Ca2+ channels

What is the first change to occur in response to a threshold stimulus?

Voltage-gated Na+ channels change shape, and their activation gates open.

The depolarization phase of an action potential results from the opening of which channels?

Voltage-gated Na+ channels.

What opens first in response to a threshold stimulus?

Voltage-gated Na+ channels.

The generation of an action potential in a neuron requires the presence what type of membrane channels?

Voltage-gated channels.

When an action potential arrives at the end of the axon terminal, a series of events take place that result in the release of neurotransmitter from the presynaptic axon. Select the answer that correctly describes the primary stimulus for vesicles to move toward the cell membrane and eventually release their contents.

Voltage-gated membrane channels open, and Ca+2 enters the cytoplasm, increasing intracellular calcium.

All of the muscles that originate from the medial epicondyle of the humerus have one of two functions. Which of the following pairs is correct?

Wrist flexion and forearm pronation. All of the muscles that originate from the medial epicondyle of the humerus are involved in either wrist flexion and forearm pronation.

Which membrane potential occurs because of the influx of Na+ through chemically gated channels in the receptive region of a neuron?

excitatory postsynaptic potential